Production and studies of properties of nanopowders on the basis of CeO2

Abstract

Nanopowders (NPds) of pure CeO2 of a specific surface area up to 210 m2/g and those doped with copper, carbon, and iron (≤1 wt % of dopant) of a specific surface area in the range 130–160 m2/g have been produced by evaporation with a pulsed electron beam. According to the X-ray phase analysis data, no secondary phases (aside from the cubic CeO2 phase) were found in the produced NPds. All the powders contained fine- and coarse-crystalline fractions differing in the size of their coherent scattering region (CSR) and in their amorphous component. The degree of crystallinity of the powders was not above 22%. The powders have a fractal structure and consist of agglomerates of sizes from dozens to hundreds of nanometers formed by crystalline nanoparticles (NPts) 3–5 nm in size with a very narrow particle size distribution. NPds have a high structural defectiveness degree, which was reflected in their magnetic properties. The room ferromagnetism was established in NPds of pure CeO2 − x and those doped with nonmagnetic elements (carbon and copper): here the ferromagnetic state in the CeO2-C system was established for the first time, whereas the magnetic moment on the carbon atom was 35-fold lower than the theoretical estimation. The ferromagnetic contribution to CeO2 NPd increases with a decrease in the NPt size and reaches 0.1 emu/g in CeO2-Fe NPd (x Fe = 0.54 wt %). It has been established that there is no direct dependence between magnetization and the content of iron ions in the CeO2-Fe-based NPds.